Donald Trump fires back at Theresa May, but tweets the wrong person

US President Donald Trump failed at sending a fiery tweet to the UK Prime Minister, accidentally directing it at the wrong person.

"Theresa @theresamay, don't focus on me, focus on the destructive Radical Islamic Terrorism that is taking place within the United Kingdom. We are doing just fine!" he tweeted, tagging someone who was not the real Theresa May.

The tweet has now been deleted, and a new tweet has been sent that tags the official account of the UK leader.

Earlier on Wednesday, Ms May criticised Mr Trump for sharing three inflammatory, anti-Muslim tweets published by a member of the far-right extremist group Britain First.

"It is wrong for the President to have done this," a spokesman for Ms May said.

"Britain First seeks to divide communities through their use of hateful narratives which peddle lies and stoke tensions. They cause anxiety to law-abiding people.

"British people overwhelmingly reject the prejudiced rhetoric of the far-right which is the antithesis of the values that this country represents: decency, tolerance and respect."

One of the tweets linked to a video claiming to show a Muslim migrant beating up a man on crutches, which has been proven false by the Netherlands Embassy.

The Embassy said the man was born and raised in the Netherlands, and had served time for his crime.

Jayda Fransen, a leader of Britain First, posted the tweets on Wednesday (local time). The other two claimed to show a group of Muslim people beating a teenage boy to death and a Muslim destroying a Christian statue.